CMP is a technology used in the fabrication of advanced memory and logic devices for a wide range of applications. The pure substrate surface and complex surface of semiconductor wafer, dielectric layer, conducting wire and barrier materials in the integrated circuits have to be polished to achieve a certain degree of planarity, which is extremely important to reach a high density of integrated circuits. In general, CMP technology consists of three specific key components including polisher, consumables (pad and slurry), and post-CMP clean. The CMP slurry provides a chemical environment to wet and adjust the interaction between abrasive, pad and the wafer surface, and also moderates the mechanical force on the polishing surface. The slurry plays a key role in CMP process and determines the production efficiency and product quality.
The present invention relates generally to the preparation of semiconductor devices and more particularly to improved slurry compositions for the CMP of metal (e.g., Cu) layers and barrier materials (e.g., Ta, TaN, etc.).
Surface planarity is of paramount importance in microelectronics. With the integrated technology approaching the era of Ultra Large Scale Integration (ULSI), CMP is touted as the only viable technique to meet today's planarity requirements. Some of the most important issues in CMP today include dishing and erosion, corrosion, defects of the surface, the control of polishing rate and selectivity among different materials on the surface. The prior art attempts to accomplish these goals as follows.
U.S. Pat. No. 4,959,113 discloses a method of polishing metal surfaces with aqueous slurries. The slurry composition comprises water, abrasive such as SiO2, Al2O3, TiO2, ZrO2, CeO2, SnO2, SiC, TiC, and a salt containing any cation of group IIA, IIIA, IVA, or IVB and any anion of chloride, bromide, iodide, nitrate, sulfate phosphate, or perchlorate. The patent also discloses a pH range of 1-6 adjusted with mineral acids.
U.S. Pat. No. 5,084,071 discloses the CMP slurry, which comprises abrasive particles, e.g. SiO2, CeO2, Fe2O3, SiC, Si3N4, containing less than 1% (w/w) of alumina, a transition metal chelated salt (e.g. EDTA) as a polishing accelerator.
U.S. Pat. No. 5,114,437 discloses the CMP slurry for polishing aluminum substrate, which contains an alumina with an average particle size of 0.2-0.5 μm, and a polishing accelerator from the group consisting of chromium (III) nitrate, lanthanum nitrate, ammonium cerium (III) nitrate and neodymium nitrate.
U.S. Pat. No. 5,209,816 discloses a method for polishing Al— or Ti-containing metal layer with the CMP slurry, which contains inorganic abrasive materials, 0.1-20% by volume of H3PO4 and 1-30% by volume of H2O2.
U.S. Pat. No. 5,225,034 discloses the CMP slurry for polishing copper layer on a semiconductor wafer to produce copper wire on the wafer. The slurry comprises AgNO3, inorganic abrasive particles and an oxidant selected from H2O2, HClO, KClO, K2MnO4, or CH3COOOH.
U.S. Pat. No. 5,340,370 discloses the CMP slurry for polishing tungsten or tungsten nitride film, which comprises an oxidizing agent such as potassium ferricyanide, inorganic abrasive particles, water, and has a pH in 2-4.
U.S. Pat. No. 5,366,542 discloses a CMP slurry comprising alumina abrasive particles, chelating agent selected from the group consisting of polyaminocarboxylic acid (EDTA) and sodium or potassium salts, and further may contain boehmite or aluminum salt.
U.S. Pat. No. 5,391,258 discloses CMP slurry for polishing silicon, silica or silicate composite. The slurry comprises, in addition to inorganic abrasive particles, hydrogen peroxide and potassium hydrogen phthalate.
U.S. Pat. No. 5,516,346 discloses CMP slurry for titanium film. The slurry contains potassium fluoride, inorganic abrasive particles such as silica, and pH<8.
U.S. Pat. No. 5,527,423 discloses the slurry for polishing a metal layer, which comprises an oxidizing agent such as iron nitrate, alumina particles containing at least 50% gamma phase, nonionic surfactants such as polyalkyl siloxanes, or polyoxyalkylene ethers.
U.S. Pat. No. 6,171,352 discloses a CMP slurry which contains, in addition to inorganic abrasive particles, an abrasion accelerator, wherein the abrasion accelerator comprises monocarboxy group- or an amino group-containing compound and optionally a nitrate salt, also a viscosity modifier such as polyacrylic acid or its copolymer.
U.S. Pat. No. 6,258,721 discloses a CMP slurry of using diamond particles as an abrasive material, comprising ingredients such as an oxidizing agent, chelating agent, surfactant and others.
All of the above reported CMP slurries employ inorganic particles as abrasive materials and fail to adequately control dishing and erosion, corrosion, defects of the surface, polishing rate and selectivity among different materials on the surface.
Another approach to preparing CMP slurries is to use organic polymeric particles as the abrasive material. Such organic polymeric particle containing abrasive materials are disclosed in U.S. Pat. No. 6,620,215. Also, U.S. Pat. No. 6,576,554 teaches a slurry for CMP having a liquid and a plurality of polishing particles, wherein the polishing particle contains a composite particle formed by thermocompressing polymeric organic particles and inorganic particles. However, none of these patents teach or suggest the use of organic non-polymeric abrasive particles in the CMP slurries nor their unexpectedly superior properties.
In U.S. patent application Ser. No. 10/734,232, now U.S. Pat. No. 7,037,351, a set of non-polymeric organic particles are employed as abrasive materials in the formulation of metal CMP slurries. The invention emphasized the importance of surface properties of the particles and the art of formulating metal CMP slurries using such non-polymeric organic particles. This is distinct from the present invention which adds to the art by teaching abrasive particles, which are engineered so they carry specifically designed functions.